Process of spinning viscose

ABSTRACT

1. A process for the production of improved cellulosic products which comprises modifying a high maturity viscose by incorporating therein at least about 0.15 percent by weight of a polyalkylene glycol having an average molecular weight of about 300 to 7,500 and extruding while stretching the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentage of said polyalkylene glycol being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having substantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength being at least about 3.83 grams per denier.

United States Patent I Paul V. Brower; John F. Fuzelt, both of Elizabethton, Tenn.

[72] Inventors [21 1 Appl. No. 463,947

[22] Filed June 14, 1965 [45] Patented Nov. 9, 1971 [73] Assignee Beaunit Corporation New York, N.Y.

Continuation of application Ser. No. 458,018, Sept. 23, 1954, now abandoned.

[54] PROCESS OF SPINNING VISCOSE [50] Field ofSearchW Primary Examiner- Allan Lieberman Attorney-Rudolph S. Bley CLAIM: l A process for the production of improved cellulosic products which comprises modifying a high maturity viscose by incorporating therein at least about 0 15 percent by weight of a polyalkylene glycol having an average molecular weight of about 300 to 7,500 and extruding while stretching the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent byweight of zinc sulfate. said percentage of said polyalkylene glycol being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having substantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength being at least about 3.83 grams per denier. v

This application is a continuation of our prior copending application Ser. No. 458,018, filed Sept. 23, 1954, now abancloned.

The present invention relates to the production of products of regenerated cellulose and more particularly is concerned with the preparation of an improved cellulose xanthate spinning solution and an improved process of wet spinning this solution to form yarn, threads, ribbons, films, foils, etc., of

. tion of a modified viscose which will yield products having improved properties of high tenacity, as well as proper elongation and fatigue characteristics so as to render the products useful for reinforcing rubber tires, belts, and the'like.

Another object of this invention is to improve the quality of rayon threads, yarns, and the like, by means of simple and practical expedients adaptable to conventionaldiscontinuous and continuous spinning processes and apparatus. These and other objects will become apparent to those'skilled in the art from the disclosures and claims which follow.

According to the present invention, a method for preparing and spinning a modified viscose has been discovered which requires very few changes to existing spinning procedures. We have discovered that a so-called normal viscose (7.0 percent cellulose (wood pulp) and a 6.0 percent alkali, for example) can be modified by the addition thereto of a small amount of a compound from the class of polyalkylene glycols, including derivatives and mixed polymers thereof, preferably, but not necessarily, in conjunction with the addition of a water-soluble salt of the type which would function as a coagulant for the viscose in an aqueous solution thereof. When viscose so modified is spun under the optimum conditions prescribed a greatly improved product has been found to result.

While the compounds which we prefer to employ from the above classes are not, each in themselves, new to the rayon art, it was completely unexpected that their combined use in the amounts indicated as additives to viscose would produce a yarn having the especially improved qualities found to exist, and indeed that even the use of the polyalkylene glycol as the sole modifier, as described hereinafter, would also bring about a substantial improvement in yarn quality.

ln the manufacture of rayon by the viscose process, whether intended for use in the textile apparel industry or as reinforcements in rubber goods, cellulose xanthate is formed in a manner which is well understood by those skilled in the art. The xanthate is dissolved, ripened, filtered, deaerated, and extruded through suitable spinnerettes into a coagulating bath. The relation between the viscose solution and the spinning or coagulating bath is adjusted to produce yarn having the desired properties for the end use contemplated.

The change in the viscose upon ageing is referred to as a ripening process, and in general the riper the viscose, the more easily it coagulates. The degree of ripeness in more recent times is commonly set forth in terms of salt index which is determined by introducing small samples into a sodium chloride solution of different concentrations. The fresher and less ripe the viscose, the stronger the solutio niof common salt necessary to precipitate the viscose. Theterm salt point," as is used in the specification and claims whic h follow, signifies the concentration of a common salt solutior'r that just suffices 1 to coagulate a drop of viscose which is allowed to drop into it.

As is well understood in the art, the degree of ripeness most favorable to spinning is dependent upon a number of factors, and the prior art teaches the spinning of viscoses exhibiting different extremes of ripeness. in the discussion of the invention which follows the term high maturity"? is applied to a viscose in a relatively green" condition. Such green viscose possesses a high salt point, i.e., a stronger solution of sodium 'chloride is required to coagulate a drop of such viscose, hence the designation high maturity."

The present invention, as indicated, is'base'd upon the surprising discovery that a so-called normal viscose, prepared according to more or less conventional methods, can be modified by the-addition thereto of a polyalkylene glycol, and preferably also (but not necessarily a water-soluble salt of the type which would coagulate the viscose in aqueous solution. Upon spinning this viscose at arelatively high maturity in the presence of a zinc salt, a cellulosic structure having greatly improved propertiescan be obtained with dry strengths inexcess of 4 grams/den. being possible. 7

Other patent literature, too numerous to mention, also discloses the addition of polyalkylene oxides or glycols or derivatives thereof to the cellulose pulp, the viscose per se or to the spin bath to aid in the shredding and filtration steps, or as a spinning assistant.

While some of the patents with which we are familiar indicate that the addition of such polymerized compounds to the viscose or spin bath result in fewer broken filaments in the yarn, none of the patent art with which we are familiar teaches that any of the polyalkylene-glycols or derivatives thereof can be added to viscose either alone or in combination with other agents to produce a rayon yarn possessing the superior qualities possible through the practice of the present invention.

Likewise, while various ones of the so-call'ed coagulating salts with whichthe present invention is concerned have been added to viscose either alone or in combination with other'agents, they have been primarily utilized to slow down the rate of regeneration of the viscose so that the material could be stored for longer periods, or for purposes other than improving the quality of the yarn, except indirectly.

According to the present invention, it has been discovered that a polyalkylene glycol, can be added to the viscose preferably together with a salt such as sodium sulfide, and spun at a relatively high salt index into a regenerating and coagulating bath having a high concentration of zinc salt, such as zinc sulfate, to produce a rayon yarn having improved properties of tenacity, optimum elongation and ratio of dry to wet strength, to name a few. in more detail, my invention comprises the modification of a so-called normal viscose by the ad dition thereto of a polyalkylene glycol such as Carbowax 4000," in an amount in excess of the normally accepted amounts required to prevent spinnerette incrustation, and preferably also (but not necessarily) a water-soluble salt such as sodium sulfide in an amount in excess of that normally produced as a byproduct in the dexanthation and regeneration of the viscose when such byproduct salts are selected for use. As indicated, the so-called modified viscose is spun at a high maturity into a regeneration bath having a relatively high concentration of zinc salt on the order of 4 to 8 percent.

The high maturity or salt index required for the optimum spinning of the modified viscose of the present invention may be obtained by cooling the freshly prepared viscose to a temperature in the neighborhood of 4 C. and then allowing the viscose to gradually warm up until the correct salt point is reached for delivery to the spinning machines. The optimum spinning salt point can be also achieved by controlling the amounts of CS used in the step of xanthation. Since too high a CS content is undesirable in spinning a high quality yarn product, any increase in the CS used to reach the required salt point should be as slight as possible. By cooling within the range of 10 not to l6 C. and in the case of the upper temperature limit, maintaining the temperature until delivery to the spinning machines, or in the case of the lower limit of 10 C., permitting a slight warming up of the viscose prior to spinning the optimum salt point for spinning can be likewise reached. When employing the above median cooling temperatures, it is only necessary to increase the CS, employed in xanthating very slightly in order to spin at the optimum degree of maturity, and the additional CS required within this range of cooling has been found not to be seriously objectionable. For economic reasons, cooling temperatures much below 10 C. introduces problems which might require expensive modifcations to conventional equipment and therefore make the lower cooling temperature objectionable from this standpoint. However, when cooling to 4 C. during ageing is employed, only about 35 CS is required in xanthating. When cooling to the high temperature, up to 40 CS, is required in xanthating in order to spin at the required salt point.

While an improved yarn product can be obtained at different degrees of maturity, it has been found that the greatest improvement in yarn qualities is obtained from the modified viscose of the present invention by spinning at a salt point or index of 7.5 to 9.0, with the conventional acid regeneration bath having a zinc salt content of from 4 to 8 percent and a temperature of 50 to 60 C., although higher or lower spinning temperatures are permissible. It will be appreciated by those skilled in the art that in order to spin at this optimum salt point, an index in excess of 9.0 must be attained during the initial viscose ageing period hence the necessity of either increasing the CS content or cooling to the lower temperature. From practical considerations cooling within the range of 10 to 16, with proper adjustments in the amount of CS employed to reach the optimum salt point, is preferred.

The examples which follow illustrate the manner and mode of carrying out the present invention and the highly desirable improvements in the yarn properties which result from the addition of the additives to the viscose of the present invention prior to spinning.

EXAMPLES EXAMPLE 1 A viscose spinning solution was prepared, as follows, employing a wood pulp. This pulp was steeped in dip lye containing 266 g./l. alkali at a temperature of 20 C. for 50 minutes. The press was drained for 3 minutes and the pressure on the pulp sheets held 5 minutes. The alkali cellulose so prepared was shredded for 90 minutes with an end temperature of 26- 30" C. The shredded pulp was aged for 24 hours at 16-18 C. The pulp, so treated, contained 33.6 percent cellulose and 15.5 percent alkali. The aged pulp was sulfidized with 35 CS (based on cellulose in alkali cellulose) for a period of 2 hours at a temperature of 25 C. and the resulting xanthate crumbs dissolved in a 12 percent water/lye solution. During the dissolving step, 5.52 percent technical grade sodium sulfide and 0.25 percent Carbowax 4000 were added to the mass (both percentages based on cellulose in alkali cellulose). The resulting 7 percent cellulose, 6 percent alkali viscose so produced was cooled to a temperature of 4 C. and allowed to gradually warm up to room temperature prior to spinning. This viscose was spun into a coagulating bath containing 120 g./1. sulfuric acid, 213 g./l. sodium sulfate and 101 g./l. zinc sulfate. The viscose, at time of spinning, possessed a salt point of 8.4 (NaCl) and a spinning viscosity of 50 (ball fall). The viscose was spun through a spinnerette having 0.075 mm. hole sizes with a depth of immersion in the coagulating bath of 9 inches. The freshly extruded threads were subjected to a net stretch of 70 percent and taken up to a 20 m./min. The yarn possessed a total denier of 1635 and had a dry strength of4. 19 g./den., a wet strength of 2.54 g./den., a dry elongation of 11.7, a wet elongation of 16.3 and a wet to dry ratio of 0.553. The crystallinity was 40.3 percent. Samples of this yarn were made up into an 1 H10 cable construction which possessed a strength of3.46 g./den. and a breaking elongation of 16.0. The fatigue and heat resistance were considered good.

EXAMPLE 2 A viscose was prepared as in example 1 with the exception acid, 238 g./l. sodium sulfate and 112 g./l. zinc sulfate at a temperature of 52-53 C. A spinnerette having 0.075 mm. hole sizes was employed immersed 9 inches in the coagulating bath. A net stretch of 72.3 percent was given the yarn at a takeup speed of 20 m./min. The total denier of this yearn was l637.8 with a dry strength of 4.38 g./den. The wet strength was 2.95 g./den. and the elongation dry was 12.2 and the wet elongation was 20.0 percent. The wet to dry ratio was 0.673 and the crystallinity 35.3 percent. An 1 H10 cord construction prepared from this yarn showed a dry strength of 3.80 g./den. and a breaking elongation of 18.0. The cable loss was 14.1 percent and the fatigue and heat stability were considered good.

EXAMPLE 3 A viscose prepared as in example 1, was spun at a salt point of 8.2 and a spinning viscosity of 62 into a coagulating bath containing 1 10 g./l. sulfuric acid, 212 g./l. sodium sulfate and g./l. zinc sulfate at a temperature of 52-53 C. A 0.075 mm. hole size spinnerette was employed, immersed to a depth of 9% inches in the coagulating bath. A net stretch of 70.0 percent was given to this yarn which was taken up at a speed of 19.9 meters/min. After completion of the customary aftertreatments, the yarn exhibited a total denier of 1656.7 and a dry strength of 4.32 g./den., a wet strength of 2.54 g./den., elongation dry of 10.7 percent, elongation wet of 17.2 percent and wet to dry ratio of 0.588. The crystallinity was 44.6 percent.

EXAMPLE 4 A viscose was prepared as in the preceding examples with the exception that only 4.83 percent sodium sulfide was added and the CS increased to 35.9 percent. The viscose at spinning possessed a salt point of 8. 2and a spinning viscosity of 48 (ball fall). The coagulating bath had the following composition: 1 10 g./l. sulfuric acid, 177 g./l. sodium sulfate, g./l. zinc sulfate and was heated to a temperature of 5253 C. A 0.075 mm. spinnerette hole size was employed, immersed to a depth of 9 /2 inches in the coagulating bath. The yarn was subjected to a net stretch of 81.9 percent at a takeup speed of 19.9 m./min. The total denier of this yarn, after receiving the customary aftertreatment, was 1649 and possessed a strength of 4.11 g./den. dry and a wet strength of 2.64 g./den., a dry elongation of 10.7 percent, a wet elongation of 16.7 percent and a wet to dry ratio of 0.642. The crystallinity was 33.8 percent. Samples of this yarn were cabled in an 1 H10 cable construction and possessed the following characteristics; dry'strength of 3.59 g./den., elongation at the break of 14.8 percent, cable loss of 23.7 percent, and a U.S. Rubber Co. fatigue test rating of 69 hours.

EXAMPLE 5 A viscose was prepared in the manner of example 1 with the exception that 5.0 percent sodium trithiocarbonate was substituted for the sodium sulfide and 37.0 percent CS was employed in the sulfidizing step. This viscose was spun at a salt point of 8.1 with spinning viscosity of 58 (ball fall) into a coagulating bath having 114 g./l. sulfuric acid, 246 g./l. sodium sulfate and l 14 g./1. zinc sulfate at a temperature of 52- 53 C. The same spinnerette and depth of immersion as in example l was employed. A net stretch of 65.2 percent was given the yarn at a takeup speed of 19.9 m./min. This yarn, after being aftertreated and dried, possessed a total denier of 1666.6, a dry strength of 4.07 g./den., a wet strength of 2.63 g./den., a dry elongation of 12.5 percent, a wet elongation of 17.3 percent and a wet to dry ratio of 0.646. 2. crystallinity was 32.5 percent. An 1 1/10 cord construction prepared from this yarn showed a dry strength of 3.49 g./den., an elongation at the break at 18.0 percent and a U.S. Rubber Company fatigue test rating of 144.2 hours.

EXAMPLE 6 A viscose was prepared in the manner of example 1, with the exception that 2.0 percent sodium sulfite was substituted for the sodium sulfide. This viscose was spun at a salt point of 8.0 and a spinning viscosity of 51 (ball fall) into a coagulating bath containing 1 g./l. sulfuric acid, 246 g./l. sodium sulfate and 100 g./l. zinc sulfate at a temperature of 5253 C. The same spinnerette and depth of immersion was employed as in example 5. A net stretch of 72.3 percent was given the yarn at a takeup speed of m./min. Upon being aftertreated and dried, this yarn possessed a total denier of 1688, a dry strength of 3.97 g./den., a wet strength of 2.56 g./den., a dry elongation of 10.7 percent, a wet elongation of 17.5 percent and a wet to dry ratio of 0.645. The crystallinity was 36.1 percent. An 1 1/10 cord construction prepared from this yarn showed a strength of 3.36 g./den. dry and 2.95 g./den. wet with an elongation at the break of 17.0 percent. A rating of 92 hours on the U.S. Rubber Company fatigue tester was recorded.

EXAMPLE 7 A wood pulp was employed in making a viscose as set forth in the preceding example 1. Thirty-seven percent CS, was employed in the sulfidizing step and 5.52 percent technical grade sodium sulfide and 0.25 percent Carbowax 4000 were added at the time of mixing. The viscose so prepared was spun at a salt point of 7.2 with a spinning viscosity of 103 (ball fall) into a coagulating bath containing I 1 1 g./l. sulfuric acid, 215 g./1. sodium sulfate and 102 g./1. zinc sulfate at a temperature of 53 C. A 0.075 mm. spinnerette immersed 9% inches in the spin bath was employed. The yarn was given a net stretch of 62.5 percent at a spinning speed of 20 m./min. The yarn, upon being aftertreated and dried, exhibited a total denier of 1636.9, a dry strength of 4.23 g./den., a wet strength of 2.56 g./den., a dry elongation of 10.5 percent, a wet elongation of 16.5 percent and a wet to dry ratio of 0.605. The crystallinity was 47 percent. A cable construction prepared from this yarn was considered about equal in properties to that prepared from the previous examples.

EXAMPLE 8 v A 7 percent cellulose, 6 percent alkali viscose was prepared in the manner of example 1, with the exception that 5.52 sodium sulfide and 0.25 percent of a mixed polymer of ethylene and propylene oxide, was added to the viscose which was sulfidized with CS This viscose was spun at a salt point of 8.3 and a spinning viscosity of 41 (ball fall) into a coagulating bath containing 108 g./l. sulfuric acid, 214 g./l. sodium sulfate and 101 g./l. zinc sulfate at a temperature of 52 C. A 0.075 mm. spinnerette immersed to a depth of 9 inches in the spin bath was employed. The yarn was given a net stretch of 51.5 percent at a spinning speed of 20 m./min. After being washed and dried, the yarn exhibited a total denier of 1634.9, a dry strength of 4.03 g./den., a wet strength of 2.29 g./den., a dry elongation of 13 percent and a wet elongation of 18 percent with a wet to dry ratio of 0.568. The crystallinity was 43.9 percent. Physical characteristics of cords constructed as in the previous examples were considered good.

EXAMPLE 9 A 7 percent cellulose, 6 percent caustic soda viscose was prepared having incorporated therein 5.52 percent technical grade sodium sulfide and 0.25 percent of a mixed polymer of ethylene and propylene oxides. The viscose was prepared with 35 CS and was spun at a salt point of 8.0 and a spinning viscosity of 54 (ball fall) into a coagulating bath containing 108 g./l. sulfuric acid, 213 g./l. sodium sulfate and 99 g./l. zinc sulfate at a temperature of 505 C. A 0.075 mm. spinnerette immersed 9 inches in the spin bath was employed. The yarn was given a net stretch of 51.5 percent at a spinning speed of 20 m./min. and after washing and drying, showed a total denier of 1664.9 with a dry strength of 4.09 g./den., a wet strength of 2.25 g./den., and dry elongation of 13 percent, wet elongation of 16.7 percent, giving a wet to dry ratio of 0.550. The crystallinity was 43.2 percent. The cable properties were considered good.

EXAMPLE 10 A 7 percent cellulose, 6 percent caustic soda viscose prepared in the manner of example 1 was modified by the ad'- dition of 5.5 2 percent technical grade sodium sulfide and 0.15 percent Carbowax 4000 at the time of mixing. Thirty-five percent CS: was employed in the xanthation step. This viscose was spun at a salt point of 8.4 and a spinning viscosity of 59 (ball fall) into a coagulating bath containing 1 20 g./l. sulfuric acid, 213 g./l. sodium sulfate, 101 g./l. zinc sulfate at a temperature of 55 C. The viscose was extruded through a spinnerette having 0.075 mm. hole sizes and immersed 9 inches in the coagulating bath. The resulting yarn was given a net stretch of 70 percent at a spinning speed of 20 m./min. and after washing and drying exhibited a total denier of 1659.6, a dry strength of 4.10 g./den., awet strength of 2.46 g./den., with a dry elongation of 1 1.7 percent and a wet elongation of 16.3 percent yielding a wet to dry ratio of 0.600. The crystallinity was 47.8 percent. An 1 1/10 cord construction prepared from this yarn showed a dry strength of 3.45 g./den. and a wet strength of 2.98 g./den. with a'breaking elongation of 16.0 percent.

EXAMPLE 1 1 A viscose was spun of the same composition as in example 10 except for the incorporation of 0.20 percent Carbowax 4000 instead of 0.15 percent. This yarn, after being washed and dried, gave a total denier of 1658.6 and a dry strength of 4.1 1 g./den., a wet strength of 2.48 g./den., with a dry elongation of 11.3 percent, and a wet elongation of 16.5 percent yielding a wet to dry ratio of 0.603. The cable properties of this yarn were considered good.

EXAMPLE 12 A viscose was spun of the same composition as example 10 except that 0.30 percent Carbowax 4000 was employed. Yarn produced from this viscose showed a total denier of 1638.8 upon being aftertreated and dried. The dry strength was 4.16 g./den., wet strength 2.47 percent g./den., elongation dry 1 1.8 percent, elongation wet 16.8 percent with a wet to dry ratio of 0.594. The crystallinity was 30.1 percent. The cable properties of this yarn were good.

EXAMPLE 13 To illustrate the superior results obtainable by the process of the present invention, a 7 percent cellulose, 6 percent caustic soda viscose was prepared with 35 CS and no additives. This viscose was spun at a salt point of 8.0 with a spinning viscosity of 62 (ball fall) into a coagulating bath containing 129 g./1. sulfuric acid, 133.7 g./l. sodium sulfate and 164.8 g./l. zinc sulfate at a temperature of 55 C. 0.075 mm. spinnerettes, immersed to a depth of 9% inches in the spin bath, were employed. The yarn was given a net stretch of 65.2 percent and a spinning speed of 20 m./min. and after washing and drying, yielded a total denier of 1654.7 and a dry strength of 3.02 g./den., a wet strength of 1.99 g./den., a dry elongation of 13.0 percent, a wet elongation of 14.3 percent, yielding a wet to dry ratio of0.571. The crystallinity was 33.9 percent.

EXAMPLE 14 To illustrate the substantially improved results obtained by the use of a polyalkylene glycol alone over the results obtained without the polyalkylene glycol, a 7 percent cellulose, 6 percent caustic soda viscose was prepared employing 37 CS with 0.25 percent Carbowax 4000 being added to the viscose at the time of mixing. This viscose was spun at a salt point of 8.1 with a spinning viscosity of 57 (ball fall). A coagulating bath, containing 1 l l g./l. sulfuric acid, 239 g./l. sodium sulfate, 83 g./ 1. zinc sulfate and heated to a temperature of 55 C. was employed. The viscose was spun through a 0.075 mm. spinnerette which was immersed to a depth of 9% inches in the coagulating bath. The yarn was given a net stretch of 72.3 percent at a spinning speed of 20 m./min. After washing and drying, the yarn possessed a total denier of 1662.6 with a dry strength of 3.83 g./den., a wet strength of 237 gJden. and dry elongation of 10.7 percent with a wet elongation of 17.2 percent yielding a wet to dry ratio of 0.619. The crystallinity was 36.2 percent. Upon comparing the dry strength value here with the dry strength value of example 13 wherein polyalkylene glycol was not employed, an improvement of or nearly 27 percent; is evident.

EXAMPLE l 5 A 7 percent cellulose, 6 percent caustic soda viscose prepared with 39.5 CS was modified by the incorporation of 6.22 percent technical grade sodium sulfide without other additives. This viscose was spun at a salt point of 8.3 and a spinning viscosity of 48 (ball fall). A coagulating bath containing 110 g./l. sulfuric acid, 145 g./l. sodium sulfate and 164 g./1. zinc sulfate at a temperature of 55 C. was employed. This viscose was spun through a 0.075 mm. spinnerette immersed to a depth of 9% inches in the coagulating bath. This yarn was given a net stretch of 86.6 percent at a spinning speed of 19.9 m./min. After washing and drying, this yam possessed a total denier of 1617 and a dry strength of 3.86 g./den., a wet strength of 2.34 g./den., a dry elongation of 8.2 percent, a wet elongation of 12.8 percent yielding a wet to dry ratio of 0.606. The crystallinity was 3.8 percent.

The theory as to why these additives result in such markedly improved yarn is not entirely understood. It has been observed that the rate of regeneration of viscose so modified is not slowed down as might be expected from the prior art teachings relative to the addition of salts of the type covered by the present invention. In accordance with prolonged visual observation of the spinning of viscose as modified according to the present invention, the rate of regeneration remains relatively unaffected over that of the so-called normal viscoses and, if anything, was observed to be speeded up slightly.

One factor of importance, which in some measure might contribute to the improved properties of yarn produced according to the present invention, resides in an increase in the crystallinity of the yarn when the modified viscose is spun in its green condition. This is contrary to the results obtained by spinning a Carbowax modified viscose at normal maturity. Of perhaps greater importance, X-ray diffraction examinations of the yarns produced as herein described show a more needlelike crystal formation disposed along the linear axis of the yarn filaments, which in some measure might explain the increased tenacity and fatigue resistance of cords prepared from my improved yarn. Also, it can be hypothesized that the added salts, when employed, serve in part as a buffer when the viscose is extruded into the acid spin bath so that coagulation is favored over regeneration, allowing the yarn to remain in a plastic condition long enough to enable a greater stretch, with better orientation of molecular structure of the yarn threads resulting.

None of the above theories can fully account for the surprising improvement in yarn qualities which are obtained, and it is probably a combination of the above factors plus still others which are unknown to us. It should be pointed out, however, that under the spinning conditions as set forth in the above examples, the salt plus the polymeric glycol are both required in the viscose to achieve the maximum improvement as regards high tenacity. However, a considerable improvement in tenacity results from the addition of the polyalkylene glycol alone to the viscose under the spinning conditions prescribed herein, as will be observed from a comparison of the results of example 14 with those of example 13.

While the modified viscose of the present invention may be employed to produce shaped articles such as yarns and threads having properties which make them ideally suited for use as tire cord or reinforcing agents for other rubber products, it is to be understood that a highly improved rayon yarn, suitable for textile apparel purposes can be produced according to the present invention.

While polyethylene glycol having an average molecular weight of 3,000 to 3,700, is the preferred polymeric material for the practice of the present invention, it should be pointed out that good results have been obtained by the use of homologues such as polypropylene glycol and addition products of polyethylene glycol as well as certain mixed polymers of polyethylene and polypropylene glycol. While the preferred range of molecular weights of these compounds has 3,700, set forth as being between 3,000 and 3.700 corresponding to Carbowax 4000, the lower molecular weight compounds of the Carbowax class having an average molecular weight as low as 300 or 600 as well as the higher molecular weights up to an average molecular weight of 7,500 may likewise be employed, however, the preferred compound is Carbowax 4000. These polyalkylene glycols, also called polyalkylene oxides, may be represented by the structure: HO--(Cl-l Cl-l0--),,Cl-l CH OH in which n represents a whole number. They may be etherified or esterified and used in place of the plain polyalkylene glycols..Such compounds are disclosed for example in U.S. Pat. No. 2,359,750 to Collins.

While sodium sulfide has been, in general, employed in the examples as the water soluble salt of the type which in aqueous solution is a coagulant for viscose, this particular compound is preferred purely for economic reasons and not necessarily because of superior performance. Many other similar salts such as sodium sulfite, sodium thiosulfate, sodium trithiocarbonate, sodium acetate, sodium phosphate, and ammonium sulfide, to mention a few, are equally efiicacious. The salt is added to the viscose in an amount of from 4.5 to 6.50 percent based on the cellulose content of the viscose. The additives of the present invention may be added to the viscose at any stage of the viscose preparation from steeping with alkali to just prior to spinning, but we prefer the addition of the additives at the time of forming the spinning solution from the cellulose xanthate crumbs, since, at this time, the compounds are completely and thoroughly dispersed throughout the xanthate mass. it should also be pointed out that when both additives are employed the additives do not have to be added simultaneously, but can be added separately at different stages if desired, though as pointed out, the simultaneous addition at the time of mixing is preferred.

in the preceding discussion of the invention, it is indicated that the polyethylene glycol is added in amounts in excess, of that normally required as a spinning assistant to reduce spinnerette incrustations. While the teachings of the prior art indicate a rather wise possible range in the amount required for this purpose, in general less than 0.10 of a percent is required as a spinning assistant and the present invention envisions the addition of amounts in excess of such quantities on the order of 0.15 percent to 1 percent based on the amount of cellulose in the viscose.

A small initial concentration of Carbowax 4000 may be made to the spin bath prior to commencement of spinning operations as a spinning assistant if desired. This is on the order of 0.025 percent but can be varied to some extent. The addition of the Carbowax to the spin bath has been found to be of definite aid to the spinning operation.

In the specification and claims, the designation polyalkylene glycol is intended to cover the polymerization products of ethylene oxide, the homologues, substitution and addition products thereof, and in particular, propylene oxide.

As indicated in the objects set forth for the invention, our modified viscose can be spun with conventional equipment,

and is adaptable to either the one or two bath spool spinning method, as well as centrifugal pot machinesor continuous machines of the type disclosed in Bley et al. U.S. Pat. No. 2,898,627 for example, assigned to the present assignee.

ln referring to the quantities of water-soluble salts, such as sodium sulfide, to be employed, the amount used'was of technical grade, dry flake and contained'6O percent chemically pure salt. Also, the designation alkali as employed in the specification and claims in describing the water soluble salts is used in the broad sense and is intended to include the ammonium radical. Modifications and variations of this invention will be recognized readily by those skilled in'the art and we desire to include all variations and modifications coming within the scope of the appended claims.

We claim:

l. A process for the production of improved cellulosic products which comprises modifying a high maturity viscose by incorporating therein at least about 0.15 percent by weight of a polyalkylene glycol having an average molecular weight of about 300 to 7,500 and extruding while stretching the resultant viscose at a salt'point of about 7.5 to 9'into anacid spin bath comprising sulfuric acid, sodium'sulfate and at least 4 percent by weight of zinc sulfate, said percentage of said polyalkylene glycol being based upon the cellulose content of the viscose, and said amount of said polyalkylene'glycol being sufficient to produce a regenerated cellulosic product having substantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength'beingat least about 3.83 grams per denier.

2. A process following claim 1 in which said polyalkylene glycol is a polyethylene glycol having a molecular weight of at least 2,000.

3. A process for the production of high-tenacity regenerated cellulose products which comprises modifying a highmaturity viscose by incorporating therein'at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight ofa water-soluble viscose coagulant and extruding the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentages of said polyalkylene glycol and coagulant being based upon the cellulose content of said viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

4. A process following claim 3 in which the viscose coagulant is an alkali metal sulfide.

5. A process following claim 3 in which said polyalkylene glycol is polyethylene oxide having a molecular weight of at least 3,000.

6. A high maturity viscose solution having salt point of about 7.5 to 9 containing at least about 0.15 percentby weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed in viscose during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

7. A high maturity viscose having a salt point ofabout 7.5 to 9 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight ofabout 300 to 7,500 and about 4.5 to 6.5 percent by weight of an alkali metal sulfide in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed therein during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

8. A viscose solution having a salt point of about 7.5 to 9 containing at least about 0.15 percent of a polyethylene glycol having a molecular weight of about 4,000 and about 4.5 to 6.5 percent by weight of sodium sulfide in addition to thesodium sulfide and other sulfur containing compounds inherently formed therein during its preparation and maturing, said percentages being based upon the cellulose content of said viscose solution, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

9. A process for the production of viscose rayon which comprises preparing a spinning solution consisting essentially of viscose and from about 0.5 percent to 1 percent of a polyethylene glycol having an average molecular weight of about 400 to 7,500, and extruding while stretching .the

resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodiumsulfate and from about 4 percent to 15 percent by weight of 'zinc sulfate, said percentage of said polyethylene glycol being based on the cellulose content of the viscose, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyethylene glycol, said dry strength being at least about 3.83 grams per denier.

10..A process for the production of viscose rayon which comprises preparing a spinning solution consisting essentially of viscose and a small amount of apolyethylene glycol having an average molecular weight of about 400 to 7,500, and extruding while stretching the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodium sulfate and from about 4 percent to 15 percent by weight of zinc sulfate, said small amount of said polyethylene glycol, being sufficient to increase the tensile strength of the viscose rayon, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyethylene glycol, said dry strength being at least about 3.83 per denier.

11. A process for the production of improved cellulosic products which comprises modifying a high maturity viscose by incorporating therein at least about 0.15 percent by weight of a polyalkylene glycol having an average molecular weight of about 300 to 7,500 and extruding while stretching the resultant viscose at a salt point of at least 7. Zinto an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentage of said polyalkylene glycol being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength being at least about 3.83 grams per denier.

12. A process following claim 11 in which said polyalkylene glycol is a polyethylene glycol having a molecular weight of at least 2,000.

13. A process for the production of high-tenacity regenerated cellulose products which comprises modifying a high maturity viscose by incorporating thereinv at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant and extruding the resultant viscose at a salt point of at least 7. 2 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentages of said polyalkylene glycol and coagulant being based upon the cellulose content of said viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

14. A process following claim 13 in which the viscose coagulant is an alkali metal sulfide.

15. A process following claim 13 in which said polyalkylene glycol is polyethylene oxide having a molecular weight of at least 3,000.

16. A high maturity viscose solution having a salt point of at least 7.2 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed in viscose during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

17. A high maturity viscose having a salt point of at least 7.2 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight of an alkali metal sulfide in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed therein during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

18. A viscose solution having a salt point of at least 7.2 containing at least about 0. l percent by weight of a polyethylene glycol having a molecular weight of about 4,000 and about 4.5 to 6.5 percent by weight of sodium sulfide in addition to the sodium sulfide and other sulfur containing compounds inherently formed therein during its preparation and maturing, said percentages being based upon the cellulose content of said viscose solution, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.

19. A high maturity viscose solution having a salt point of at least 7.2 containing at least 0. 15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500, said percentage being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength being at least about 3.83 grams per denier.

20. A high maturity viscose solution having a salt point of at least 7.2 containing at least 0.15 percent by weight of a polyethylene glycol having a molecular weight of about 300 to 7,500, said percentage being based upon the cellulose content of the viscose, and said amount of said polyethylene glycol being sufi'lcient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyethylene glycol, said dry strength being at least about 3.83 grams per denier.

i I! 0 t 

1. A PROCESS FOR THE PRODUCTION OF IMPROVED CELLULOSIC PRODUCTS WHICH COMPRISES MODIFYING A HIGH MATURITY VISCOSE BY INCORPORATING THEREIN AT LEAST ABOUT 0.15 PERCENT BY WEIGHT OF A POLYALKYLENE GLYCOL HAVING AN AVERAGE MOLECULAR WEIGHT OF ABOUT 300 TO 7,500 AND EXTRUDING WHILE STRETCHING THE RESULTANT VISCOSE AT A SALT POINT OF ABOUT 7.5 TO 9 INTO AN ACID SPIN BATH COMPRISING SULFURIC ACID, SODIUM SULFATE AND AT LEAST 4 PERCENT BY WEIGHT OF ZINC SULFATE, SAID PERCENTAGE OF SAID POLYALKYLENE GLYCOL BEING BASED UPON THE CELLULOSE CONTENT OF VISCOSE , AND SAID AMOUNT OF SAID POLYALKYLENE GLYCOL BEING SUFFICIENT TO PRODUCE A REGENERATED CELLULOSIC PRODUCT HAVING SUBSTANTIALLY INCREASED DRY STRENGTH OVER THAT OBTAINED WITHOUT SAID POLYALKYLENE GLYCOL, SAID DRY STRENGTH BEING AT LEAST ABOUT 3.83 GRAMS PER DENIER.
 2. A process following claim 1 in which said polyalkylene glycol is a polyethylene glycol having a molecular weight of at least 2,
 000. 3. A process for the production of high-tenacity regenerated cellulose products which comprises modifying a high maturity viscose by incorporating therein at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant and extruding the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentages of said polyalkylene glycol and coagulant being based upon the cellulose content of said viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 4. A process following claim 3 in which the viscose coagulant is an alkali metal sulfide.
 5. A process following claim 3 in which said polyalkylene glycol is polyethylene oxide having a molecular weight of at least 3,
 000. 6. A high maturity viscose solution having salt point of about 7.5 to 9 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7, 500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed in viscose during the preparation and maturing thereof, said Percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 7. A high maturity viscose having a salt point of about 7.5 to 9 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7, 500 and about 4.5 to 6.5 percent by weight of an alkali metal sulfide in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed therein during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 8. A viscose solution having a salt point of about 7.5 to 9 containing at least about 0.15 percent of a polyethylene glycol having a molecular weight of about 4,000 and about 4.5 to 6.5 percent by weight of sodium sulfide in addition to the sodium sulfide and other sulfur containing compounds inherently formed therein during its preparation and maturing, said percentages being based upon the cellulose content of said viscose solution, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 9. A process for the production of viscose rayon which comprises preparing a spinning solution consisting essentially of viscose and from about 0.5 percent to 1 percent of a polyethylene glycol having an average molecular weight of about 400 to 7,500, and extruding while stretching the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulfuric acid, sodium sulfate and from about 4 percent to 15 percent by weight of zinc sulfate, said percentage of said polyethylene glycol being based on the cellulose content of the viscose, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyethylene glycol, said dry strength being at least about 3.83 grams per denier.
 10. A process for the production of viscose rayon which comprises preparing a spinning solution consisting essentially of viscose and a small amount of a polyethylene glycol having an average molecular weight of about 400 to 7,500, and extruding while stretching the resultant viscose at a salt point of about 7.5 to 9 into an acid spin bath comprising sulphuric acid, sodium sulfate and from about 4 percent to 15 percent by weight of zinc sulfate, said small amount of said polyethylene glycol, being sufficient to increase the tensile strength of the viscose rayon, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyethylene glycol, said dry strength being at least about 3.83 per denier.
 11. A process for the production of improved cellulosic products which comprises modifying a high maturity viscose by incorporating therein at least about 0.15 percent by weight of a polyalkylene glycol having an average molecular weight of about 300 to 7,500 and extruding while stretching the resultant viscose at a salt point of at least 7.2 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentage of said polyalkylene glycol being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a sUbstantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength being at least about 3.83 grams per denier.
 12. A process following claim 11 in which said polyalkylene glycol is a polyethylene glycol having a molecular weight of at least 2,000.
 13. A process for the production of high-tenacity regenerated cellulose products which comprises modifying a high maturity viscose by incorporating therein at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7,500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant and extruding the resultant viscose at a salt point of at least 7.2 into an acid spin bath comprising sulfuric acid, sodium sulfate and at least 4 percent by weight of zinc sulfate, said percentages of said polyalkylene glycol and coagulant being based upon the cellulose content of said viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 14. A process following claim 13 in which the viscose coagulant is an alkali metal sulfide.
 15. A process following claim 13 in which said polyalkylene glycol is polyethylene oxide having a molecular weight of at least 3,000.
 16. A high maturity viscose solution having a salt point of at least 7.2 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7, 500 and about 4.5 to 6.5 percent by weight of a water-soluble viscose coagulant in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed in viscose during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 17. A high maturity viscose having a salt point of at least 7.2 containing at least about 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7, 500 and about 4.5 to 6.5 percent by weight of an alkali metal sulfide in addition to the alkali metal sulfides and other sulfur containing compounds inherently formed therein during the preparation and maturing thereof, said percentages being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 18. A viscose solution having a salt point of at least 7.2 containing at least about 0.15 percent by weight of a polyethylene glycol having a molecular weight of about 4,000 and about 4.5 to 6.5 percent by weight of sodium sulfide in addition to the sodium sulfide and other sulfur containing compounds inherently formed therein during its preparation and maturing, said percentages being based upon the cellulose content of said viscose solution, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a dry strength of at least about 3.83 grams per denier.
 19. A high maturity viscose solution having a salt point of at least 7.2 containing at least 0.15 percent by weight of a polyalkylene glycol having a molecular weight of about 300 to 7, 500, said percentage being based upon the cellulose content of the viscose, and said amount of said polyalkylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyalkylene glycol, said dry strength being at least about 3.83 grams per denier.
 20. A high maturity viscose Solution having a salt point of at least 7.2 containing at least 0.15 percent by weight of a polyethylene glycol having a molecular weight of about 300 to 7, 500, said percentage being based upon the cellulose content of the viscose, and said amount of said polyethylene glycol being sufficient to produce a regenerated cellulosic product having a substantially increased dry strength over that obtained without said polyethylene glycol, said dry strength being at least about 3.83 grams per denier. 